These investigators will have three main objectives relevant to the chemistry and function of neurofilament proteins: 1, the determination of the partial sequence of the immuno-reactive, cyanogen bromide peptide from the neurofilament protein in order that its sequence may be directly compared between different mammals and to substantiate its use as a soluble peptide characteristic of this protein for quantitative immunologic measurement; 2, the comparison to establish similarities or differences between the neurofilament protein and the glial fibrillary protein, tonofilaments and other 10 nm diameter proteins found in various cells; 3, the determination of the class of fibrillar proteins that proliferates in neurons under treatment with neurolathyrogens. The immunologic crossreactivity already demonstrated between preparations of glial fibrillary protein and neurofilament protein requires a definitive investigation of the relationship between these proteins and, because other 10 nm proteins have aroused interest in other cells, the difference between these various classes is a matter for urgent investigation in order that the definition of the cellular function of these proteins may be clearly determined. BIBLIOGRAPHIC REFERENCES: Davison, P. F.: An appraisal of radioiodination methods for peptide mapping. Anal. Biochem. 75, 129 (1976). Hong, Bor-Shyue and Davison, Peter F.: Isolation and Characterization of the antigenic peptide of calf brain neurofilament protein. Federation Proceedings, (FASEB) 36, abstract 2520, p. 751 (1977).